This invention relates to a coating apparatus, and more specifically to an apparatus for coating one side of one or more strips or tapes of any such materials as woven or nonwoven fabrics, plastics, paper, foam products, etc. The coating apparatus of this invention is of particular utility when used for applying a coating material of relatively high viscosity to the rear sides of elongate surface type fastener tapes having a multiplicity of hooks or loops on their front sides, in order to firmly anchor such hooks or loops to their carrier fabric.
The surface type fastener is known which comprises one fastener member having a multiplicity of hooks on a piece of carrier fabric, and another fastener member having a multiplicity of loops on another piece of carrier fabric. When pressed against each other, the two fastener members fasten together as a result of the interengagement of the hooks and loops. The hooks and loops are disengageable when the fastener members are forced apart. In the manufacture of such surface type fasteners, fastener tapes are prepared which are elongate strips of carrier fabric each having hooks or loops on its front side. The rear sides of these fastener tapes must be coated with a fluid material that, on curing, can provides a positive anchorage for the hooks or loops onto the carrier fabric against the possibility of detachment in use.
"Kiss roll coating" and "dip coating" represent two familiar methods of coating surface type fastener tapes or like strips. "Kiss roll coating" is such that the coating roller, partly immersed in a coating liquid in an open top vessel, carries a film of the liquid on its exposed upper portion. As the strip of substrate material travels in contact with the coating roller, part of the film transfers to the strip. In "dip coating", on the other hand, the strip to be coated is immersed in a vessel of coating material.
These conventional methods can both provide coatings of uniform thickness if the coating material is of relatively low viscosity. However, if the coating material is of higher viscosity, its layer on the desired strip tends to be of uneven thickness, particularly in cases where the strip to be coated is so pliant as to readily twist, bend or otherwise go out of planar shape while being coated.
The doctor blade has been a common expedient for applying high viscosity coating materials to surface type fastener tapes and other strips. For example, as taught by Japanese Laid Open Patent Application No. 59-228970, a strip or strips to be coated are fed in contact with a coating roller against which a doctor blade is held. The doctor blade is movable for adjustably varying the gap between itself and the coating roller, in order to form a metered film of the coating material on the roller. An objection to this prior art apparatus is that it has no provisions for guiding the strip as the same travels in contact wtih the coating roller. The strip is therefore easy to twist or bend while being coated, due in part to the minute variations in the diameter of the coating roller and to the oscillations of the revolving shaft on which it is mounted. The result has been irregularities in the thickness of the coating in the longitudinal direction of the strip.
The instant applicant is aware of a prior art device having means for positively guiding the strip being coated, as suggested by Japanese Laid Open Patent Application No. 59-80355. This known device, however, is applicable only for coating the longitudinal edge portions of the strip and is not adaptable for coating its complete surface.